The purpose of the project is to determine if the pattern of discharge of motor units is altered in aging man. The discharge of motor units of the abductor digiti minimi muscle of normal young subjects (20-30 years old) will be compared to that of normal older subjects (50-80 years). The activity of the motor units, detected by implanted fine wire electrodes will be studied during maintained isometric contractions, linearly increasing and decreasing isometric contractions and resisted isotonic contractions. The amplitude, frequency at recruitment, frequency during sustained isometric contractions. The amplitude, frequency at recruitment, frequency during sustained isometric contractions, peak frequency, frequency upon dropping a motor unit potential. The characteristics of discharge of units from each decade will be compared to that of other decades. It is anticipated that the patterns of discharge of motor units for the young and older subjects will be different because of alterations in the nervous system with age. Older subjects may have smaller motor units and/or a reduction in the number of units due to random denervation of muscle fibers. In addition, the remaining innervated muscle fibers may not behave normally, because themotor pathways controlling movement are affected by age and may be unable to drive the muscle fibers as before. If an individual displays abnormalities in the behavior of his motor units, the production of tension by the involved muscle will also be abnormal, therefore, the results of this study could lead to a greater understanding of the mechanisms which underlie the weakness, slowness, and incoordination which occur with old age.